Add the rehash utility to the openssl CLI tool

[smittals2]

Description of changes:

Adding the rehash utility to the OpenSSL CLI tool. This design makes a number of different design choices from OpenSSL. Namely:

1. Multiple directory paths are not supported, therefore duplicate filenames are not supported
2. Like OpenSSL, any existing symlinks matching the hash regex are removed from the given directory. We do not provide an option to preserve these.
3. We return a binary true or false to indicate status. OpenSSL counts and returns the number of errors.
4. Simplified the general processing logic and hash table structures.
5. Removed windows filesystem support, we only need this tool for unix based systems.
6. We don't support the legacy hash format (MD5)

Testing:

PENDING

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